Stabilizing solutions for submicronic particles, methods for making the same and methods of stabilizing submicronic particles

ABSTRACT

Stabilizing solutions for submicronic particles, methods for making the same and methods of stabilizing submicronic particles is disclosed.

This application is a division of U.S. patent application, Ser. No.11/547,987 filed Oct. 5, 2006, now U.S. patent No. ______ which is 371of PCT/IN2005/000,153 filed may, 11, 2005.

FIELD OF THE INVENTION

This invention relates to nano submicronic particles and particularly,it relates to a stabilizing solution for submicronic particles, methodsfor making these stabilizing solutions and methods of stabilizingsubmicronic particles to form stable nano submicronic particles.

BACKGROUND OF THE INVENTION

Submicronic particles are particles less than 1 micron and include nanoscale particles.

Nano particles are part of an emerging science called ‘nano technology’.The word nano technology comes from the Greek prefix ‘nano’ meaning “onebillionth”. In modern scientific parlance, a nanometer is one billionthof a meter, about the length of ten hydrogen atoms placed side by sidein a line. The smallest things that an unaided human eye can see are10,000 nanometers across. Nano particles are typically and generallyspherical in shape.

Nanoscience, simply, is the study of the fundamental principles ofstructures with at least one dimension roughly between 1 and 100nanometers and Nanotechnology is the application of these nanostructuresinto useful nanoscale devices.

Nano scale particles of substances exhibit properties unlike theproperties of their macro counterparts often with stunning new results.Nano scale is unique because it is the size scale where the familiarday-to-day properties of materials like conductivity, hardness ormelting point meet the more exotic properties of the atomic andmolecular world such as wave-particle duality and quantum effects. Atthe nano scale, the most fundamental properties of the materials andmachines depend on their size in a way they don't at any other scale.For e.g. a nano scale wire or circuit component does not necessarilyobey Ohm's law. Nano-scale particles have unique physical properties(e.g. optical, dielectric, magnetic, mechanical), transport properties(e.g., thermal, atomic diffusion) and processing characteristics (e.g.,faster sintering kinetics, super-plastic forming).

Physicist Richard Feynman first described the possibility of molecularengineering. In 1959 Feynman gave a lecture at the California Instituteof Technology called “There's Plenty of Room at the Bottom” where heobserved that the principles of physics do not deny the possibility ofmanipulating things atom by atom. He suggested using small machines tomake even tinier machines, and so on down to the atomic level itself.Nano technology as it is understood now though, is the brainchild ofFeynman's one-time student K. Eric Drexler. Drexler presented his keyideas in a paper on molecular engineering published in 1981, andexpanded these in his books Engines of Creation and Nano systems:Molecular Machinery, Manufacturing and Computation, which describes theprinciples and mechanisms of molecular nano technology.

In 1981 the invention of the Scanning Tunneling Microscope or STM, byGerd Binnig and Heinrich Rohrer at IBM's Zurich Research Labs, and theAtomic Force Microscope (AFM) five years later, made it possible to notonly take photos of individual atoms, but to actual move a single atomaround. Soon after, John Foster of IBM Almaden labs was able to spell“IBM” out of 35 xenon atoms on a nickel surface, using a scanningtunneling microscope to push the atoms into place.

A nanometer is a magical point on the dimensional scale. Nano structuresare at the confluence of the smallest of Human-made devices and thelargest molecules of the living things. Nano technology exploits the newphysical, chemical and biological properties of systems that areintermediate in size, between isolated atoms/molecules and bulkmaterials, where the transitional properties between the two limits canbe controlled.

The synthesis and characterization of nano particles has receivedattention in recent years because of the possibility of their widespreaduse in industry and chemistry. Nanotechnology is gaining importance inareas such as biomedical sciences, optics, electronics, magnetics,mechanics, ceramics, catalysis and energy science. However, thepreparation of such nano structured materials poses several uniquechallenges. A range of nano particles has been produced by physical,chemical and biological methods.

Two approaches have been adopted for nano fabrication—The Top downprocesses, which include the methods of synthesis that carve out or addaggregates of molecules to a surface. The second is the bottom upapproach, which assembles atoms or molecules into nano structures.

PHYSICAL methods include Electron beam lithography, Scanning probemethod, Soft lithography, Microcontact printing, Micromoulding.

In Electron Beam Lithography, an electron beam scans the surface of asemiconductor containing a buried layer of quantum well material. Theresist gets removed where the beam has drawn a pattern.

Soft lithography is an extension of the previous technique and overcomesthe impracticability of applying electron beam lithography to largescale manufacturing by making a mould or a stamp, which can be usedrepeatedly to produce nanostructures. In Micro contact printing, thePDMS stamp is inked with a solution consisting of organic moleculescalled thiols and then pressed against a thin film of gold on a siliconplate. The thiols form a self-assembled monolayer on the gold surfacethat reproduces the stamp pattern; features in the pattern can be assmall as 50 nm. In Micromoulding, the PDMS stamp is placed on a hardsurface, and a liquid polymer flows into the recesses between thesurface and the stamp. The polymer solidifies into the desired pattern,which may contain features smaller than 10 nm.

Scanning probe microscope can image the surface of conducting materialswith atomic scale detail. Hence single atoms can be placed at selectedpositions and structures can be built to a particular pattern atom byatom. It can also be used to make scratches on a surface and if thecurrent flowing from the tip of the STM is increased the microscopebecomes a very small source for an electron beam which can be used towrite nanometer scale patterns. The STM tip can also push individualatoms around on a surface to build rings and wires that are only oneatom wide.

In Sonochemical method, an acoustic cavitation process is used togenerate a transient localized hot zone with extremely high temperaturegradient and pressure (Suslick et al. 1996). Such sudden changes intemperature and pressure bring about the destruction of the sonochemicalprecursor (e.g., organometallic solution) and the formation ofnanoparticles.

Hydrodynamic cavitation consists of synthesis of Nanoparticles bycreation and release of gas bubbles inside sol-gel solutions (Sunstromet al. 1996).

High energy ball milling is already a commercial technology, but hasbeen considered dirty because of contamination problems fromball-milling processes. However, the availability of tungsten carbidecomponents and the use of inert atmosphere and/or high vacuum processeshave reduced impurities to acceptable levels for many industrialapplications. Common drawbacks include the low surface area, the highlypolydisperse size distributions, and the partially amorphous state ofthe as prepared powders.

CHEMICAL methods include Wet chemical preparation, Surface passivation,Core shell synthesis, Organometallic precursor, Sol gel method,Langmuir-Blodgett method, Precipitation in structured media, Zeolites,Micelles and inverse micelles formation.

A number of chemical strategies are now available for the constructionof higher order structures. Organic molecules can be linked together bymolecular recognition. For example, synergistic noncovalent donoracceptor interactions can give rise to intertwined rings (catenanes).Liquid crystal polymers having self-organized structures can be formedfrom organic molecules containing head groups capable of complementaryhydrogen bonding interactions. Organic molecules can be assembled aroundmetal ions such as Cu (I) that provide stereo chemical constricts in theconstruction of double helices. The synthesis of inorganic clusters, bycontrast, is usually dependent on passivating the surface of a growingaggregate by capping the surface sites with stabilizing ligands.

Wet Chemical Preparation method involves the reaction between a metalion and the desired anion under controlled conditions to generatenanocrystals of desired size.

BIOLOGICAL methods include Biomineralization using Bacteria, Yeast,Fungi, Plants and Biotemplating using Ferritin, Lumazine synthase, VirusSurface layers DNA etc.

A few attempts have been made to synthesize sulfides, typically cadmiumsulfide (CdS) using microorganisms. It was shown that CdS nanoparticlescan be synthesized in the yeasts Candida glabrata andSchizosaccharomyces pombe. These nanoparticles are coated with shortpeptides known as phytochelatins, which have the general structure(y-Glu-Cys)n-Gly where n varies from 2-6. The nanoparticles are sizereproducible, more monodisperse, and have greater stability thansynthetically produced nanoparticles. Further work on microbialsynthesis of CdS nanoparticles is scant and is limited to studies oncharacterization and efficient production in batch cultivation.

U.S. Pat. Nos. 5,876,480 & 6,054,495 describe a process for creatingunagglomerated metal nanoparticles, comprising the steps of

-   -   (a) forming a dispersion in an aqueous or polar solvent, the        dispersion including unpolymerized lipid vesicles, the        unpolymerized lipid vesicles each comprising at least one lipid        bilayer, the lipid bilayer including a negatively charged lipid        that has an anionic binding group, and the lipid vesicles having        catalytic first metal ions bound thereto by ionic bonding,    -   (b) combining the dispersion of step (a) with a metallization        bath containing free second metal ions to form a mixture, and    -   (c) incubating the mixture of step (b) at a temperature        sufficient to reduce said free second metal ions and to form        unagglomerated metal nano-particles having an average diameter        between about 1-100 nm.

U.S. Pat. No. 6,068,800 describes a process and apparatus for producingnano-scale particles using the interaction between a laser beam and aliquid precursor solution using either a solid substrate or a plasmaduring the laser-liquid interaction.

U.S. Pat. Nos. 5,618,475 and 5,665,277 relate to production ofparticulates having nanoparticle dimensions, such as about 100nanometers diameter or less, and, more particularly, to apparatus andmethod for producing nanoparticles of metals, alloys, intermetallics,ceramics, and other materials by quench condensation of a hightemperature vapor generated by an evaporator having features effectiveto isolate evaporation conditions from downstream conditions and toconcurrently evaporate materials of dissimilar vapor pressures.

U.S. Pat. No. 5,736,073 describes a process of production of nanometerparticles by directed vapor deposition of electron beam evaporant onto asubstrate.

U.S. Pat. No. 6,706,902 The continuous process according to theinvention includes impregnating support materials and, after thermalactivation, drying the support materials by spraying or by fluidized bedtechnology leads to form precious metal-containing support compositionsthat are active in the catalysis of oxidation reactions.

U.S. Pat. No. 6,562,403 is broadly concerned with chemical methods offorming ligated nanoparticle colloidal dispersions and recovered ligatednanoparticles which may be in superlattice form.

U.S. Pat. No. 5,698,483 A process for producing nano size powderscomprising the steps of mixing an aqueous continuous phase comprising atleast one metal cation salt with a hydrophilic organic polymericdisperse phase, forming a metal cation salt/polymer gel, and heattreating the gel at a temperature sufficient to drive off water andorganics within the gel, leaving as a residue a nanometer particle-sizepowder.

The main disadvantages of these methods are that they are expensive andtechnically difficult and too slow for mass production. Most of thetechniques are also capital intensive as well as inefficient inmaterials and energy use. The known methods are difficult to control inorder to acquire a desired size and shape of the nano-scale particles tobe produced. Many of these synthesis techniques also require the use ofa vacuum unit and involve environmental concerns about chemical wastedisposal. Almost all of the methods used in the manufacture ofsubmicronic scale particles use at least one toxic or questionablechemical reagent at any of the three main components of synthesis whichare solvent medium used in the synthesis, the reducing agent used in thesynthesis and the material used for stabilization. Most of the reportedmethods rely heavily on the use organic solvents. Particles made withthe help of these solvents are not biocompatible and thereforeunsuitable for use in biological applications such as biosensors andmarkers. Many of the reducing agents such the borohydrides,dimethylformamide, hydrazines are very highly reactive chemicals and arehazardous both environmentally and biologically. In some cases isolationand recovery of the particles is difficult for example in the case ofsurfactants which have an affinity for carbon dioxide. The mostsignificant set of problems arise however in the step of stabilization.Almost all the stabilizing or capping agents used in the form ofpolymers or chemicals pose hazardous and risky steps either in the finalstabilized product or in the process of making the stabilizing substanceor in the process of stabilization.

Physical and chemical methods in the manufacture of nanoparticlesinvolve controlling crystallite size by restraining the reactionenvironment. However, problems occur with general instability of theproduct and in achieving monodisperse size. The dispersion of nanoparticles usually display very intense color due to plasmon resonanceabsorption, which can be attributed to the collective oscillation ofconduction electrons, induced by the presence of an electromagneticfield.

Other problem areas in the above mentioned methods are uniformdistribution of particles, morphology and crystallinity, particleagglomeration during and after synthesis and separation of theseparticles from the reactant.

Nano particles are extremely reactive as the coordination of surfaceatoms in nano particle is incomplete, and can lead to particleagglomeration to minimize total surface or interfacial energy of thesystem. This problem is overcome by passivating the bare surface atomswith protecting groups. Capping or passivating the particle not onlyprevents agglomeration, it also protects the particles from itssurrounding environment, and provides electronic stabilization to thesurface. The capping agent usually takes the form of a Lewis basecompound covalently bound to surface metal atoms.

Chemical techniques have therefore been developed to passivate orstabilize these nano particles. It is desirable that nano particles areprotected from the environment but are still allowed to maintain theirintrinsic properties. It has been shown that the size, morphology,stability and properties (chemical and physical) of these nanoparticleshave strong dependence on the specificity of the preparation method andexperimental conditions.

The stabilizing of nano particles in a sub micronic regime requires anagent that can bind to the cluster surface and thereby uncontrolledgrowth or agglomeration of the cluster or discrete particles into largerparticles is prevented. The simplest method involves the use of asolvent that acts as a stabilizer of the small clusters. Unagglomeratednano particles can also be made by the use of polymeric surfactants andsstabilizers added to a reaction designed to precipitate a bulk material.The polymer attaches to the surface of the growing clusters and eitherby steric or electrostatic repulsion prevents further growth of the nanoclusters. Commonly used chemical stabilizers include sodiumpolyphosphate and anionic agents such as thiolates.

Most capping reactions involve additional steps and the capping agentsare generally toxic substances.

It is an object of the present invention to provide a stabilizingsolution that successfully retains the intrinsic physical and chemicalproperties of the individual submicronic and particularly nano scaleparticles molecules.

Another object of this invention is to provide an inexpensive andenvironmental friendly process for manufacturing a stabilizing solutionand to an efficient and ‘green’ process for the stabilizing ofsubmicronic particles.

According to this invention therefore there is provided a sub micronicparticle stabilizing solution comprising an aqueous extract of maceratedbiological cells having pH of 5.5 to 7.5, open circuit potential between+0.02 to +0.2 volt, temperature between 20 degrees to 30 degrees Celsiusand concentration of total organic carbon being at least 18,000 ppm.

Typically, the biological cells are plant cells of plant tissue selectedfrom a group of tissues comprising living tissue of leaves, fruits,stems, roots and flowers and parts thereof.

Alternatively, the biological cells are animal cells of animal tissueselected from a group of tissues consisting of tissues of worms,insects, fishes, mollusks, crustaceans, and higher animals.

Still alternatively, the cells are microbial cells selected from a groupof microbes, which include bacteria, fungi, yeasts, viruses, protozoaand algae.

In accordance with another aspect of this invention there is provided amethod of making a submicronic particle stabilizing solution whichcomprises the steps of

{a} obtaining fresh biological tissue;{b} macerating the biological tissue in water to form a suspensioncontaining the extracts of the biological tissue;{c} removing from the suspension suspended particles greater than onemicron to obtain a clear concentrated extract;{d} diluting the concentrated extract with deionized water in a ratioranging from the original to 1:10 dilution;{e} adjusting the temperature to 25 degrees Celsius;(f) adjusting the pH of the diluted extract to between 5.5 to 7.5 pH;{g} measuring the open circuit potential to ensure that that potentiallies within the range of +0.02 to 0.2 volt; and{h} measuring the total organic carbon content to ensure that thecontent is at least 18,000 parts per million in solution.

The biological tissue is typically, macerated by at least one methodfrom a group of macerating methods which consists of grinding, blending,milling, microwave treatment, ultrasonication, sonication, pounding,pressure extrusion, freezing-thawing, irradiation, heat treatment,osmolysis, enzymatic lysis, chemical lysis, vacuum lysis, anddifferential pressure lysis.

The removal of suspended particles is achieved by filtering thesuspension through a sub micronic filter element.

In accordance with a preferable embodiment of the invention, the aqueousextract is treated with a non polar solvent, such as n-cyclohexane forbeneficiation of the biomolecules in the extract.

In accordance with still another aspect of this invention there isprovided a method of stabilizing sub micronic particles which comprisesthe steps of

dispersing sub micronic particles in the stabilizing solution inaccordance with this invention to obtain a resultant in which theconcentration of the particles ranges from 5 to 300 ppm; andmixing the resultant for a period of 30 minutes to three hours to obtaina suspension of stabilized solid sub micronic particles.

In accordance with yet another aspect of this invention there isprovided a method of stabilizing sub micronic metal particles, duringtheir synthesis, which comprises the steps of

dispersing salt of the metal in deionized water to form a solution;adding the formed solution to the stabilizing solution in accordancewith this invention to obtain a resultant in which the concentration ofthe metal is in the range from 5 to 300 ppm and the effective dilutionof the stabilizing solution is in the range of 1:1 to 1:10;adding a reducing agent to the resultant; andmixing the resultant for a period of 30 minutes to three hours to obtaina suspension of stabilized solid submicronic particles.

Typically, the sub micronic particles are particles selected from agroup of particles from transition metals, alkali metals, alkaline earthmetals, rare earth metals, metalloids, a combination of metals, metalliccompounds and the sub micronic particles are nano particles and thestabilizing solution is added during the synthesis of the nano particlesby a process from a group of process which includes a chemical process,a physical process and a biological process or after the synthesis.

In accordance with one embodiment of this invention the sub micronicparticles are silver ions and the step includes dispersing a silver saltin deionized water having conductivity of less than 3 micro siemens.

In accordance with another embodiment of the invention, the sub micronicparticles are gold ions and the step includes dispersing a gold salt indeionized water.

Typically, the reducing agent is at least one reducing agent selectedfrom a group containing the stabilizing solution, citric acid,borohydride, sodium sulfide sodium acetate.

The theoretical considerations underlying the invention are as follows:

In nature, the chemical composition of cells across flora and fauna areremarkably similar. Thus living plants cells are very similar chemicallyto animal cells and microbial cells.

All cells contain biomolecules such as polysaccharides, proteins, lipidsand nucleic acids which are made up of building blocks such asmonosaccharides, amino acids, fatty acids, nucleotides. In addition manydynamically acting molecules such glutathione, cytochromes, ubiquinone,NADH, FADH, pyruvic acid, citric acid, maleic acids, glycerol are alsopresent. These biomolecules have various reactive groups such assulfhydryl, amino, imino, carboxyl, hydroxyl, and the like.

When living cells are macerated in water the biomolecules are releasedin the water. These biomolecules collectively contain all the reactivegroups where the elements are in specific proportion to each other. Ithas been found that these biomolecules have the surprising collectiveability to not only reduce metal ions such as gold and silver but alsoto act sterically on metal nano particles so as to stabilize them eitherin the process of their synthesis or in a post synthesis process. Thebinding interaction between biomolecules is relatively weak as comparedwith the interaction between these particles and typical chemicalcapping agents such thiols.

Metal nanoclusters are optically transparent and act as dipoles.Conduction and valence bands of metal nanoclusters lie closely andelectron movement occurs quite freely. The potential applications ofthese systems are mainly associated with unusual dependence of theoptical and electronic properties on the particle size. Silver particleshaving 5-50 nm sizes show a sharp absorption band in the 410-420 nmregions. While the same phenomenon with gold nano particles are observedat 520-550 nm.

The size of metal particles prepared by the method described inaccordance with this invention depend on the concentration of the metalions and concentration of biomolecules.

The synthesis of a particle, requires a two-step process, i.e.,nucleation followed by successive growth of particles. In accordancewith the present invention where the stabilization solution is addedduring the synthesis in the first step, part of metal ions in solutiongets adsorbed on free nucleophilic groups (—SH, OH, NH₂) present on thesurface of biomolecules in the stabilizing solution and get reduced. Thereduced metal atoms thus created act as nucleation centers andfacilitate further reduction of metal ions present in the bulk solution.The atomic coalescence leads to the formation of metal clusters and canbe controlled by the natural ligands and surfactants forming part ofbiomolecular mass. Thus biomolecules act as both reducing as well asstabilizing agent. It has been found that a threshold concentrationvalue of biomolecular mass is required to seed the process ofsubmicronic formation and stabilization. This is expressed in terms ofthe total organic carbon content of the biomolecular mass.

It has also been found by experimentation that the reduction potentialplays an important and crucial part in the formation and stabilizationof nano particles, particularly, gold and silver nano particles. Theelectromotive force exhibited by 1 M concentration of a reducing agentand its oxidized form at 25° C. and pH 7.0 is called its standardreduction potential. It is a measure of the relative tendency of thereducing agent to lose electrons.

The reduction potential is measured in positive or negative volts on ascale in which the positive sign denotes a lower reduction potentialthan the negative sign. Therefore a substance with a standard reductionpotential of +0.1 volt has a higher reduction potential than a substancewith a standard reduction potential of +0.2 volts and thereforesubstance with a standard reduction potential of +0.1 volts will reducethe substance having a reduction potential of +0.2 volts. The standardreduction potentials of some of the biomolecules, such as NADH,ubiquinone, cytochrome b_(k) are −0.32 Volt, −0.05 Volt and +0.03 Volt.On the other hand, the standard reduction potentials for conversion ofions such as gold and silver to their solid state are +1.5 Volt and +0.8Volt, respectively. Thus the findings in accordance with this inventionis that many biomolecules which have an effective standard reductionpotential higher than that required for the conversion gold and silverions to solid state particles, can effectively reduce these ions insolution. It is not possible to measure the standard reduction potentialof the solutions formed in this invention because the molarconcentrations of individual components of the biomolecular mass isunknown. However, dynamically the open circuit potential of the solutioncan be determined easily. At specific molar concentrations the opencircuit potential has a direct relationship with the standard reductionpotential. The open circuit potential indicates the initial empiricalredox state of the solution.

For the process of our invention, it is critical that the stabilizingsolution has an open circuit potential +0.02 to +0.2 Volt, a pH between5.5 and 7.5 and temperatures between 20 to 30 degrees Celsius are alsoimportant parameters. The total organic carbon content of thestabilizing solution must also be at least 18,000 ppm. Purity of waterhaving conductivity less than 3 micro siemens is also of significantimportance in optimizing the process of particle formation.Concentration of metal ions in the reacting solution should lie between5 to 300 ppm; metal ions in the mother solution being 150 to 60000 ppm.

It has been found in the course of experimentation that bio moleculesnormally found in plant cells, animal and microbial cells in the intactplant, animal or microbe have a reducing potential and are theirreducing ability very slowly decreases when exposed to air under ambientconditions and rapidly to denaturing treatment. The reducing ability istherefore inversely related to the freshness of the tissue. It has alsobeen found that the reducing ability varies from tissue to tissue and isinversely proportional to the duration of exposure to air eventuallytending to zero.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the plasmon peak for the silver nano particlesof Example 1.

FIG. 2 is a transmission electron microscopy of the colloidal suspensionof the product of Example 1.

FIGS. 3A and 3B are atomic force microscopies of the product of Example1.

FIG. 4 is a showing the plasmon peak for the silver none particle ofExample 2.

FIGS. 5 and 6A and 6B are the TEM and AFM studies of the product ofExample 2.

FIG. 7 is the TEM picture of the product of Example 6.

FIG. 8 is the TEM picture of the product of Example 8.

The invention will now be described with reference to the accompanyingexamples, which in no manner limit the ambit and scope of thisinvention.

EXAMPLE 1

Using Labconco, USA water pro system with pre-filter, carbon filter andreverse osmosis membrane water was collected. The said water had theconductivity of 2.7 microSiemens as measured by the online digital meterfitted in the instrument.

50 whole flowers of Hibiscus rosasinensis Linn (48.37 gm wet wt) weremacerated with 150 ml of deionized water in a blender (500 rpm) for 10minutes to get a homogenous viscous suspension. This viscous suspensionwas filtered through Whatman No 1 filter paper under vacuum to obtain aclear 165 ml of viscous solution. From this an aliquot of 10 ml wasdiluted up to 100 ml using water.

An aliquot of 7 ml were removed and checked for open circuit potentialat 25° C. on Electrochemical analyzer (CH Instruments 600B, USA) using athree-electrode system. Ag/AgCl_((aq)) was used as reference electrode,Glassy carbon as working electrode (diameter 3 mm) and Pt wire (length 4cm) as counter electrode. The value found was +0.15 Volt. Similarly pHof free flowing solution was checked using Digital pH meter (controlDynamics, India) and it was found to be 5.6.

The concentration of total organic carbon was measured using Beckman TOCanalyzer and was found to be 22,180 ppm.

The synthesis of silver nanoparticle was carried out by Borohydridereduction method as described by Jin. R, Cao. Y. W., Kelly K. L., SchatzG. C., Zheng, J. G. and Chad A. Mirkin. (2001) Photoinduced conversionof silver nanospheres to nanoprisms. Science: 294; 1901-1903. Briefly,10 ml of flower aqueous extract reacted with 100 μl of silver nitratestock solution (100 mM) followed by addition of 100 μl of sodiumborohydride (500 mM) which resulted in formation of a colloidalsuspension.

Sample of colloidal suspension was scanned from 200-800 nm using DiodeArray spectrophotometer (Ocean Optics, USA). A peak at 410 nm wasdetected. This peak was characteristic plasmon peak for silver nanoparticle [FIG. 1 of the accompanying drawings], typically having averagediameter of 5-120 nm.

Another aliquot of colloidal suspension was examined by Transmissionelectron microscopy (TEM) at 200 kV using Philips electron microscopeequipped with field emission gun, i.e., CM200 FEG. TEM specimen wasprepared by pipetting 2 μL of colloid solution onto a carbon coatedcopper grid and image was obtained. The average size seen in image was10-20 nm. [FIG. 2 of the accompanying drawings]

Atomic force microscopy (AFM) of the sample was performed using NanonicsMultiView 1000 AFM head with E scanner (Nanonics Imaging Ltd.,Jerusalem, Israel). Sample was scanned in non-contact mode with a probeof 20 nm radius and a resonance frequency of 80 kHz. AFM images werecaptured, processed and analyzed with QUARTZ software, Version 1.00(Cavendish Instruments Ltd., UK). For specimen, 5 μL of sample wasplaced on a 1-cm² glass slide (thickness 0.5 mm) and dried in laminarairflow before imaging. Uniform particles of 50-100 nm diameter and 125nm height were observed as seen in FIG. 3 a of the accompanying drawingswhich is the three dimension AFM view of a portion of the sample and 3 bis a two dimensional view showing size analysis of a typical particle].

10 ml of colloidal suspension was kept at room temperature 27° C. for 90days. At the end of 90 days spectral scan was carried out and microscopywith TEM and AFM was repeated. It was found that plasmon peak, particlesize and shape remain substantially unchanged. Thus proving that thereis no agglomeration of the nano particles.

Another 2 ml of solution was kept at 60° C. in a water bath for 30minutes and no substantial change in plasmon peak particle size andshape was observed indicating the stability of the nano particlesuspension.

Similarly another 2 ml of nano particle suspension was frozen at −70° C.and then thawed at room temperature. After thawing the sample spectralscan was carried out and microscopy with TEM and AFM was repeated. Itwas found that plasmon peak, particle size and shape remainsubstantially unchanged. Thus proving that there is no agglomeration ofthe nano particles.

Yet another 2 ml of solution was freeze dried under vacuum usinglyophilizer (Vertis Freezemobile 5EL, USA). The dried powder wasresuspended in 2 ml deionized water and spectral scan was carried outand microscopy with TEM and AFM was repeated. It was found that plasmonpeak, particle size and shape remain substantially unchanged. Thusproving that there is no agglomeration of the nano particles.

Another 2 ml of solution was centrifuged at 30,000 G for 30 min usingultracentrifugation (Optima Max centrifuge, Beckman Coulter, USA). Thepellet was resuspended in 2 ml deionized water and spectral scan wascarried out and microscopy with TEM and AFM was repeated. It was foundthat plasmon peak, particle size and shape remain substantiallyunchanged. Thus proving that there is no agglomeration of the nanoparticles.

Similarly 5 ml of nano particle suspension was buffered with citratebuffer of pH strength (3, 4, and 5) and phosphate buffer of pH strength(8, 9, 10) and kept for 30 min at the end of 30 min spectral scan wascarried out and microscopy with TEM and AFM was repeated. It was foundthat plasmon peak, particle size and shape remain substantiallyunchanged. Thus proving that there is no agglomeration of the nanoparticles.

In 5 ml of nanoparticle suspension sodium chloride was added to achievefinal concentration of 10 mM to 50 mM after 30 min of addition spectralscan was carried out and microscopy with TEM and AFM was repeated. Itwas found that plasmon peak, particle size and shape remainsubstantially unchanged. Thus proving that there is no agglomeration ofthe nano particles.

The above tests show that the silver nano particles are stable undernormal and moderately harsh environmental conditions in presence offlower extract.

EXAMPLE 2

The water having conductivity of 2.7 microSiemens was used in theexperiment and the experiment was carried out at 27 degrees celsius.

The leaves of Asparagus racemosus (47.00 gm wet wt) were macerated with150 ml of water as described in example 1 and filtered through WhatmanNo 1 filter paper under vacuum to obtain a clear 155 ml of solution.From this stock an aliquot of 10 ml was diluted up to 100 ml withdeionized water and mixed thoroughly by shaking. The open circuitpotential and pH were measured as described in example 1 and found to be+0.09 Volts and 6.0 respectively. The concentration of total organiccarbon was measured using Beckman TOC analyzer and was found to be23,480 ppm.

The synthesis of gold submicronic particles was carried out by thecitrate reduction method as described in J Turkevitch, P. C Stevensonand J Hillier, (1951). Nucleation and Growth Process in the Synthesis ofColloidal Gold. Discuss. Faraday Soc., 11, 55-75. Briefly, 10 ml leafextract was reacted with 200 μl of tri-sodium citrate solution (1%)followed by addition of 25 μl of chloroauric acid (25 mM). Samples weredrawn and checked for various parameters as described in example 1.Characteristic plasmon peak of nano gold particles at 540 nm wasobserved indicating an average diameter in the range of 20-150 nm. [FIG.4 of the accompanying drawings]. The TEM and AFM studies (FIGS. 5 and 6of the accompanying drawings confirmed nano scale submicronic particlesand average diameter was found to be 30 nm. The stability of nanoparticles was checked in detail as described in example 1 and it wasobserved that the gold nano particles are stable under normal andmoderately harsh environmental conditions.

EXAMPLE 3

Water having conductivity of 2.7 microSiemens was used in theexperiment.

Fruiting body of fungus Itajahia sp. (45 wet wt) was macerated in 150 mlof water in example 1 and filtered through Whatman No 1 filter paperunder vacuum to obtain a clear 165 ml of solution From this stock analiquot of 10 ml was diluted up to 100 ml with deionized water and mixedthoroughly by shaking The open circuit potential and pH was measured asdescribed in example 1 and found to be +0.11 Volts and 6.0 respectively.The concentration of total organic carbon was measured using Beckman TOCanalyzer and was found to be 26,800 ppm.

The synthesis of FeS nano particles was carried out by solid phasesynthesis using sodium sulphide as reducing agent as described W-XZhang, C B wang and H I Lien, (1998) Treatment of chlorinated organiccontaminants with nanoscale bimetallic particles. Catalysis Today. 47;387-395. Briefly, in 10 ml of extract FeSO₄ (0.25 M) was added followedby addition of sodium sulphide (0.25 M) and stirred vigorously undernitrogen atmosphere. To this mixture Na₂S (1 M, 5 ml) was added dropwiseto get a black colloidal suspension of FeS. The colloidal suspension wascentrifuged at 8000×g for 30 minutes at 25° C. and particles wereseparated after decanting the supernatant. They were washed severaltimes with N₂ purged deionized water to remove the unreacted components.After drying under vacuum they stored at room temperature in cleanvials. Samples were drawn and checked for various parameters asdescribed in example 1. The TEM and AFM studies confirmed submicronicparticles and average diameter was found to be 250 nm. The stability waschecked in detail as described in example 1 and it was observed that theparticles were stable under normal and moderately harsh environmentalconditions. The FeS particles retained their black color at ambienttemperature indicating the particle stability.

EXAMPLE 4

Water having conductivity of 2.7 microSiemens was used in experiment.

In yet another example flowers of Nyctanthes arbor-tristis (common name;harsingar 53.00 gm wet wt) were macerated with 150 ml of deionized wateras described in example 1. The suspension was filtered through WhatmanNo 1 filter paper under vacuum to obtain a clear 170 ml of solution.From this stock an aliquot of 10 ml was diluted up to 100 ml withdeionized water and mixed thoroughly by shaking. The open circuitpotential and pH was measured as described in example 1 and found to be+0.120 Volts and 5.8 respectively The concentration of total organiccarbon was measured using Beckman TOC analyzer and was found to be20,190 ppm.

The synthesis of copper nanoparticles in solution was carried out byphoto-reduction method as described in S Kapoor and T Mukherjee, (2003)Photochemical formation of copper nanoparticles inpoly(N-vinylpyrrolidone). Chemical Physics Letters 370; 8387. Briefly,10 ml of flower extract was reacted with 1×10⁻⁴ M CuSO₄ under the set ofconditions as described. The resulting colloidal suspension showedcharacteristic plasmon band of copper at 565 nm indicating an averagesize in range of 10-50 nm. The colloidal suspension was found to stablefor 21 days at room temperature.

EXAMPLE 5

Water having conductivity of 2.7 microSiemens was used in experiment.

Whole leaves of Aloe-vera (55.37 gm wet wt) were washed, peeled andmacerated with 150 ml of deionized water in a blender (500 rpm) for 10minutes to get a homogenous viscous suspension. This viscous suspensionwas filtered through Whatman No 1 filter paper under vacuum to obtain aclear 165 ml of viscous solution. From this stock an aliquot of 10 mlwas diluted up to 100 ml by water and mixed thoroughly by shaking to geta free flowing solution. The open circuit potential and pH was measuredas described in example 1 and found to be +0.08 Volts and 6.8respectively. The concentration of total organic carbon was measuredusing Beckman TOC analyzer and was found to be 29,300 ppm.

Synthesis of bismuth nano particles via microemulsion method was carriedout as described in J. Fang, K L Stokes, J A wienmann, W L Zhou, (2000).Nanocrystalline bismuth synthesized via an in-situpolymerization-microemulsion process. Materials Letters 42: 113-120.Briefly, 10 ml solution of aloe-vera extract was reacted with 0.03 Msolution of bismuth nitrate solution followed by the addition of 0.15 Msodium borohydride, rest of the conditions were maintained. Theresulting colloidal suspension has shown characteristic plasmon band ofbismuth at 268 nm indicating an average size in range of 10-100 nm. Thecolloidal suspension was found to stable for 21 days at room temperature

EXAMPLE 6

The water having conductivity of 2.7 microSiemens was used inexperiment.

Ripe fruits of Azadirachta indica (53.00 gm wet wt) were macerated with150 ml of deionized water as described in example 1 and seeds wasremoved. The mucilaginous suspension was filtered through Whatman No 1filter paper under vacuum to obtain a clear 170 ml of solution. Fromthis stock an aliquot of 10 ml was diluted up to 100 ml with deionizedwater and mixed thoroughly by shaking. The open circuit potential and pHwas measured as described in example 1 and found to be +0.110 Volts and6.2 respectively. The concentration of total organic carbon was measuredusing Beckman TOC analyzer and was found to be 25,400 ppm.

The synthesis of CdS nano particles was carried out by solid-statereaction as described in W Wang, Z liu, C Zheng, C Xu Y Liu, G Wang,(2003). Synthesis of CdS nano particles by a novel and simple one-step,solid-state reaction in the presence of a nonionic surfactant. MaterialsLetters 57; 2755-2760. Typically, 5.8 gm of cadmium chloride and 6.144gm of sodium sulphide was ground in presence of 10 ml of the fruitextract. The resulting suspension was centrifuged at 8000-×G for 30minutes at 25° C. and particles were separated after decanting thesupernatant. They were washed several times with deionized water toremove the unreacted components and pellet was dissolved in water. Theresulting colloidal suspension has shown characteristic plasmon band ofCdS at 468 nm indicating an average size in range of 5-10 nm as seen inthe TEM picture [FIG. 7 of the accompanying drawings]. The colloidalsuspension was found to stable for 60 days at room temperature.

EXAMPLE 7

Water having conductivity of 2.7 microSiemens was used in experiment.

Leaves of Eucalyptus camaldulensis (54 gm wet wt) were macerated with150 ml of deionized water as described in example 1. The suspension wasfiltered through Whatman No 1 filter paper under vacuum to obtain aclear 157 ml of solution. The open circuit potential and pH was measuredas described in example 1 and found to be +0.07 Volts and 6.2respectively. The concentration of total organic carbon was measuredusing Beckman TOC analyzer and was found to be 23,180 ppm.

The synthesis of nanocrystalline CeO₂ was carried out by microwaveirradiation as described in X H Liao, J Zhu, J J Zhu, J Z Xu, and H YChen, (2001) Preparation of monodispersed nanocrystalline CeO2 powdersby microwave irradiation. Chem. Commun., 937-938. Typically, 1 wt % PEG,0.01 mol L⁻¹ (NH4)₂—Ce(NO₃)₆, 1 wt % sodium acetate and 1% extract wasexposed to microwave radiation at a power level of 30% (the microwaveoperating in a 30 second cycles, on for 9 s, and off for 21 s at a totalpower of 650 W for 10 min), and then cooled to room temperature Theresulting precipitate was centrifuged, washed with distilled water anddried in air. The final yellow product was collected forcharacterization. Particles in size range of 10-20 nm were observed byTEM and rechecked for stability after 90 days.

EXAMPLE 8

Water having conductivity of 2.7 microSiemens was used in experiment.

Roots of Withania somnifera (common name Ashwagandha; 50 gm wet wt) wasmacerated with 150 ml of deionized water as described in example 1. Thesuspension was filtered through Whatman No 1 filter paper under vacuumto obtain a clear 157 ml of solution. From this stock an aliquot of 10ml was diluted up to 100 ml with deionized water and mixed thoroughly byshaking. The open circuit potential and pH was measured as described inexample 1 and found to be +0.07 Volts and 6.2 respectively. Theconcentration of total organic carbon was measured using Beckman TOCanalyzer and was found to be 24,300 ppm.

The synthesis of PbS nano particles was carried out by sulfur reductionunder heating conditions as described Jin Joo, Hyon Bin Na, Taekyung Yu,Jung Ho Yu, Young Woon Kim, Fanxin Wu, Jin Z. Zhang, and Taeghwan Hyeon,(2003) Generalized and Facile Synthesis of Semiconducting metal SulfideNanocrystals. J. AM. CHEM. SOC. 2003, 125, 11100-11105. Typically, 10 mlof extract was reacted with PbCl₂ (0.28 gm) in presence of sulphur (27mg). The particle size was found to be in the range of 5-10 nm as seenin FIG. 8 of the accompanying drawings. After 90 days the TEM image werefound to be unchanged.

EXAMPLE 9

Water having conductivity of 2.7 microSiemens was used in experiment.

Leaves of Eucalyptus camaldulensis (54 gm wet wt) were macerated with150 ml of deionized water as described in example 1. The suspension wasfiltered through Whatman No 1 filter paper under vacuum to obtain aclear 157 ml of solution. The open circuit potential and pH was measuredas described in example 1 and found to be +0.07 Volts and 6.2respectively. The concentration of total organic carbon was measuredusing Beckman TOC analyzer and was found to be 22,150 ppm.

The synthesis of ZnS nano particles was carried out by sulfur reductionunder heating conditions as described in Jin Joo, Hyon Bin Na, TaekyungYu, Jung Ho Yu, Young Woon Kim, Fanxin Wu, Jin Z. Zhang, and TaeghwanHyeon, (2003) Generalized and Facile Synthesis of Semiconducting metalSulfide Nanocrystals. J. AM CHEM. SOC. 2003, 125, 11100-11105.Typically, 10 ml of extract was reacted with ZnCl₂ (2 mM) in presence ofsulphur (6 mM). The particle size was found to be in the range of 10-30nm. The particles were found to be fluorescent when excited with UVradiation which remained unchanged after 30 days.

EXAMPLE 10

Water having conductivity of 2.7 microSiemens was used in experiment.

5 whole leaves of Aloe-vera (55.37 gm wet wt) were washed, peeled andmacerated with 150 ml of deionized water in a blender (500 rpm) for 10minutes to get a homogenous viscous suspension. This viscous suspensionwas filtered through Whatman No 1 filter paper under vacuum to obtain aclear 165 ml of viscous solution. From this stock an aliquot of 10 mlwas diluted up to 100 ml with deionized water and mixed thoroughly byshaking to get a free flowing solution. The open circuit potential andpH was measured as described in example 1 and found to be +0.07 Voltsand 6.8 respectively. The concentration of total organic carbon wasmeasured using Beckman TOC analyzer and was found to be 24,200 ppm.

The synthesis of MnS nano particles was carried out by sulfur reductionunder heating conditions as described in Jin Joo, Hyon Bin Na, TaekyungYu, Jung Ho Yu, Young Woon Kim, Fanxin Wu, Jin Z. Zhang, and TaeghwanHyeon, (2003) Generalized and Facile Synthesis of Semiconducting metalSulfide Nanocrystals. J. AM. CHEM. SOC. 2003, 125, 11100-11105.Typically, 10 ml of extract was reacted with MnCl₂ (2 mM) in presence ofsulphur (2 mM). The particle size was found to be in the range of 20-80nm.

EXAMPLE 11

49 gm of Argyeria speciosa leaves (7 in no) were macerated in a blender,in distilled water; the final volume was made up to 150 ml. This extractwas filtered through muslin cloth and further centrifuged at 5000 rpmfor 5 min to remove suspended materials before use. The open circuitpotential and pH was measured as described in example 1 and found to be+0.05 Volts and 6.8 respectively. The concentration of total organiccarbon was measured using Beckman TOC analyzer and was found to be30,200 ppm.

Synthesized gold and silver nano particles synthesized by the citratemethod and the borohydrate reduction method respectively were suspendedin 10 ml leaf extract. The resultant solution was mixed thoroughly forone hour. Samples were drawn and checked for various parameters asdescribed in example 1. Characteristic plasmon peak for gold at 540 nmindicated average diameter of the particle in the range 20 to 150 nm.For silver similar peaks were observed at 410 nm and the TEM pictureshowed nano particles in the size range of 50 120 nm. After 90 days thestability remained unchanged.

EXAMPLE 12

Bitter gourd (20 gm) was soaked in water, blended in mixer, and dilutedwith 150 ml of distilled water. Extract was obtained by pressing thepulp from muslin cloth. Prior to execution of the experiment, theextracts were filtered with Whatman No 1 filter paper and stored at 4°C. The open circuit potential and pH was measured as described inexample 1 and found to be +0.07 Volt and 6.9 respectively. Theconcentration of total organic carbon was measured using Beckman TOCanalyzer and was found to be 24,200 ppm.

Synthesis of gold and silver nano particles was effected by addingminute quantities of silver nitrate and gold chloride stock solutions[concentration 50,000 ppm and 25,000 ppm respectively] to 10 ml of thebitter gourd extract diluted 5 fold. The resultant solution was mixedthoroughly for three hours. The color of the solution changed from colorless to reddish yellow in case of silver and from golden yellow to pinkin case of gold after incubation for 3 hours. Characteristic plasmonpeak for gold at 550 nm indicated average diameter of the particle inthe range 20 to 150 mm. For silver similar peaks were observed at 420 nmand the TEM picture showed nano particles in the size range of 50 to 120nm. After 90 days the stability remained unchanged.

EXAMPLE 13

50 gms of live earth worms [Lumbricus terristris] were ground in amortar pestle and 150 ml deionized water until a homogenous viscoussuspension was formed. The viscous solution was filtered through Whatmanno 1 filter paper under vacuum to obtain a clear solution. This solutionwas diluted 10 fold and the open circuit potential and pH was measuredas described in example 1 and found to be +0.18 Volt and 7 respectively.The concentration of total organic carbon was measured using Beckman TOCanalyzer and was found to be 32,200 ppm.

Synthesis of gold and silver nano particles was effected by addingminute quantities of silver nitrate and gold chloride stock solutions[concentration 50,000 ppm and 25,000 ppm respectively] to 10 ml of theaqueous extract. The resultant solution was mixed thoroughly for onehour. Samples were drawn and checked for various parameters as describedin example 1. Characteristic plasmon peak of silver nano particles at410 nm and for gold nano particles at 530 was observed. TEM image ofsilver nano particles also confirms the formation particles in the rangeof 10-50 nm for silver and 30 to 80 for gold.

EXAMPLE 14

50 gms of fresh fish [pomfret—Pampus argentus] was ground in a tissuehomogenizer and mixed with 150 ml deionized water until a homogenousviscous suspension was formed. The viscous solution was filtered throughWhatman no 1 filter paper under vacuum to obtain a clear solution. Thissolution was diluted 10 fold and the open circuit potential and pH wasmeasured as described in example 1 and found to be +0.09 Volt and 7.2respectively. The concentration of total organic carbon was measuredusing Beckman TOC analyzer and was found to be 34,200 ppm.

Synthesis of gold and silver nano particles was effected by addingminute quantities of silver nitrate and gold chloride stock solutions[concentration 50,000 ppm and 25,000 ppm respectively] to 10 ml of theaqueous extract. The resultant solution was mixed thoroughly for onehour. Samples were drawn and checked for various parameters as describedin example 1.

Characteristic plasmon peak of silver nanoparticles at 410 nm and forgold nano particles at 530 was observed. TEM image of silver nanoparticles also confirms the formation particles in the range of 10-50 nmfor silver and 30 to 80 for gold.

EXAMPLE 15

50 gms of freshly harvested culture in pellet form of Escherichia coliwas sonicated in deionized water for 15 minutes the resultant suspensionwas centrifuged at 8000 G and the clear supernatant was diluted 10 foldand the open circuit potential and pH was measured as described inexample 1 and found to be +0.1 Volt and 6.7 respectively. Theconcentration of total organic carbon was measured using Beckman TOCanalyzer and was found to be 24,000 ppm.

Synthesis of gold and silver nano particles was effected by addingminute quantities of silver nitrate and gold chloride stock solutions[concentration 50,000 ppm and 25,000 ppm respectively] to 10 ml of theaqueous extract. The resultant solution was mixed thoroughly for onehour. Samples were drawn and checked for various parameters as describedin example 1. characteristic plasmon peak of silver nanoparticles at 420nm and for gold nano particles at 550 was observed. TEM image of silvernano particles also confirms the formation particles in the range of10-50 nm for silver and 30 to 80 for gold.

EXAMPLE 16

Water having conductivity of 2.7 microSiemens was used in experiment.

5 whole leaves of Aloe-vera (55.37 gm wet wt) were washed, peeled andmacerated with 150 ml of deionized water in a blender (500 rpm) for 10minutes to get a homogenous viscous suspension. This viscous suspensionwas filtered through Whatman No 1 filter paper under vacuum to obtain aclear 165 ml of viscous solution. To this solution 50 ml ofn-cyclohexane was added and the resultant was thoroughly shaken in aseparating funnel. The cyclohexane extract was separated and thecontents were re-extracted in 150 ml of deionized water. From this stockan aliquot of 10 ml was diluted to 200 ml with deionized water and mixedthoroughly by shaking to get a free flowing solution. The open circuitpotential and pH was measured as described in example 1 and found to be+0.11 Volts and 6.8 respectively. The concentration of total organiccarbon was measured using Beckman TOC analyzer and was found to be19,200 ppm.

Synthesis of gold and silver nano particles was effected by addingminute quantities of silver nitrate and gold chloride stock solutions[concentration 50,000 ppm and 25,000 ppm respectively] to 10 ml of theaqueous extract. The resultant solution was mixed thoroughly for onehour. Samples were drawn and checked for various parameters as describedin example 1. Characteristic plasmon peak of silver nano particles at420 nm and for gold nano particles at 550 was observed. TEM image ofsilver nano particles also confirms the formation particles in the rangeof 20-40 nm for silver and 5 to 10 for gold.

All the above examples were carried out at a temperature around 25degrees Celsius.

The examples show that the aqueous extracts of macerated cells ofbiological tissue are excellent agents for stabilization of submicronicparticles. Additionally, they are an eco friendly reducing agent in thesynthesis of gold and silver sub micronic particles.

1.-7. (canceled)
 8. A method of making a sub micronic particlestabilizing solution, which comprises the steps of (a) obtaining freshbiological tissue; (b) macerating the biological tissue in water to forma suspension containing the extracts of the biological tissue; (c)removing from the suspension suspended particles greater than one micronto obtain a clear concentrated extract; (d) diluting the concentratedextract with deionized water in a ratio ranging from the original to 1to 10 dilution; (e) adjusting the temperature to 25 degrees Celsius; (f)adjusting the pH of the diluted extract to between 5.5 to 7.5 pH; and(g) measuring the open circuit potential to ensure that that potentiallies within the range of +0.1 to +0.2 volt; and (h) measuring the totalorganic carbon content to ensure that the content is at least 18,000parts per million in solution.
 9. A method of making a sub micronicparticle stabilizing solution as claimed in claim 8, in which thebiological tissue is macerated by at least one method from a group ofmacerating methods which consists of methods, grinding, blending,milling, microwave treatment, ultrasonication, sonication, pounding,pressure extrusion, freezing-thawing, irradiation, heat treatment,osmolysis, enzymatic lysis, chemical lysis, vacuum lysis, anddifferential pressure lysis.
 10. A method of making a sub micronicparticle stabilizing solution in which the removal of suspendedparticles is achieved by filtering the suspension through a sub micronicfilter element.
 11. A method of stabilizing sub micronic particles whichcomprises the steps of (a) dispersing sub micronic particles indeionized water to form a dispersion in which the concentration of theparticles is in the range of 150 to 60000 ppm; (b) adding the dispersionto the stabilizing solution of claim 1 to obtain a resultant in whichthe concentration of the particles ranges from 5 to 300 ppm; (c) mixingthe resultant for a period of 30 minutes to three hours to obtain asuspension of stabilized solid sub micronic particles.
 12. A method ofstabilizing sub micronic metal particles, during their synthesis, whichcomprises the steps of dispersing salt of the metal in deionized waterto form a solution; adding the formed solution to the stabilizingsolution in accordance with claim 1, to obtain a resultant in which theconcentration of the metal is in the range from 5 to 300 ppm and theeffective dilution of the stabilizing solution is in the range of 1:1 to1:10; adding a reducing agent to the resultant; and mixing the resultantfor a period of 30 minutes to three hours to obtain a suspension ofstabilized solid submicronic particles.
 13. A method as claimed in claim11, where the sub micronic particles are particles selected from a groupof particles selected from transition metals, alkali metals, alkalineearth metals, rare earth metals, metalloids, a combination of metals,metallic compounds.
 14. A method as claimed in claim 11, where the submicronic particles and the stabilizing solution is added during thesynthesis of the nano particles by a process from a group of processwhich includes a chemical process, a physical process and a biologicalprocess.
 15. A method as claimed in claim 11, where the sub micronicparticles are silver ions and the step includes dispersing a silver saltin deionized water having conductivity of less than 3 micro siemens. 16.A method as claimed in claim 11, where the sub micronic particles aregold ions and the step includes dispersing a gold salt in deionizedwater.
 17. A method as claimed in claim 11, in which, the aqueousextract is treated with a non polar solvent, typically n-cyclohexane.18. A method as claimed in claim 12, in which, the reducing agent is atleast one reducing agent selected from a group containing thestabilizing solution, citric acid, borohydride, sodium sulfide sodiumacetate.